Note: Descriptions are shown in the official language in which they were submitted.
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MICROSPHERE FILLED POLYMER COMPOSITES.
Technical Field
This description relates a polymer composition containing a polymeric matrix,
microspheres, and a block copolymer and a method for producing the polymer
composition.
Background
In general, microspheres, or other conventional fillers, are often added to
polymeric
composites to either replace costly polymer components, to enhance specific
mechanical
characteristics of the overall composites, or both. The enhancements provided
by the
inclusion of the microspheres are often intended to reduce the warpage and
shrinkage or
address strength to weight characteristics of the composites. The inclusion of
hollow
microspheres often provides a reduction in the weight of the composite as
well. However,
including the microspheres generally results in a trade-off of properties in
the final
composite. The microspheres may enhance at least one physical property or
mechanical
characteristic of the composite, while adversely affecting others.
It is conventionally recognized by those of skill in the art that the addition
of
microspheres to polymeric composites results in decreased mechanical
properties such as
tensile strength and impact resistance in comparison to the polymer composite
without
microspheres. The degradation of mechanical properties is generally attributed
to the
relatively poor adhesion between the polymeric component of the composite and
the
microspheres.
Silane-based surface treatments on glass and other microspheres have been
found
to successfully reverse some of the degradation of mechanical properties
attributed to poor
adhesion between the microsphere surface and the polymeric matrix. Silanes,
however,
have a low molecular weight, thus providing no entanglement with the polymer.
Silanes
may be used to recover select mechanical properties, but results vary
depending on the
type of polymer.
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Summary
The present invention is directed to the use of block copolymers as additives
for
polymeric composites containing microspheres. The utilization of block
copolymers in
conjunction with microspheres prevents the generally recognized degradation of
mechanical properties of a polymeric composite when microspheres are used
alone. The
combination of block copolymers with microspheres in a polymeric composite may
enhance certain mechanical properties of the composite, such as tensile
strength, impact
resistance, tensile modulus, and flexural modulus.
The composition of the present invention comprises a polymeric matrix, a
plurality
of microspheres, and one or more block copolymers. The block copolymers have
at least
one segment that is capable of interacting with the microspheres. For purposes
of the
invention, the interaction between the block copolymers and the microspheres
is generally
recognized as the formation of a bond through either covalent bonding,
hydrogen bonding,
dipole bonding, or ionic bonding, or combinations thereof. The interaction
involving at
least one segment of the block copolymer and the microsphere is capable of
enhancing or
restoring mechanical properties of the polymeric matrix to desirable levels in
comparison
to polymeric matrices without the block copolymer.
The present invention is also directed to a method of forming a polymeric
matrix
containing microspheres and one or more block copolymers. The one or more
block
copolymers are capable of interacting with the microspheres.
The combination of block copolymers with microspheres has applicability in
either
thermoplastic or thermosetting compositions. The microspheres useful in the
inventive
composition include all conventional microspheres suitable for use in a
polymeric matrix.
Preferred microspheres are glass or ceramic, with a most preferred embodiment
directed to
hollow glass microspheres.
Block copolymers can be tailored for each polymeric matrix, microsphere, or
both,
adding a broad range of flexibility. In addition, multiple physical properties
can be
augmented through block design. Block copolymers can be used instead of
surface
treatments. Alternatively, the block copolymers may be used in tandem with
surface
treatments.
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Definitions
For purposes of the present invention, the following terms used in this
application
are defined as follows:
"Block" refers to a portion of a block copolymer, comprising many monomeric
units, that has at least one feature which is not present in the adjacent
blocks;
"Compatible mixture" refers to a material capable of forming a dispersion in a
continuous matrix of a second material, or capable of forming a co-continuous
polymer
dispersion of both materials;
"Interaction between the block copolymers and the microspheres" refers to the
formation of a bond through either covalent bonding, hydrogen bonding, dipole
bonding,
or ionic bonding or combinations thereof;
"Block copolymer" means a polymer having at least two compositionally discrete
segments, e.g. a di-block copolymer, a tri-block copolymer, a random block
copolymer, a
graft-block copolymer, a star-branched block copolymer or a hyper-branched
block
copolymer;
"Random block copolymer" means a copolymer having at least two distinct blocks
wherein at least one block comprises a random arrangement of at least two
types of
monomer units;
"Di-block copolymers or Tri-block copolymers" means a polymer in which all the
neighboring monomer units (except at the transition point) are of the same
identity, e.g.,
AB is a di-block copolymer comprised of an A block and a B block that are
compositionally different and ABC is a tri-block copolymer comprised of A, B,
and C
blocks, each compositionally different;
"Graft-block copolymer" means a polymer consisting of a side-chain polymers
grafted onto a main chain. The side chain polymer can be any polymer different
in
composition from the main chain copolymer;
"Star-branched block copolymer" or "Hyper-branched block copolymer" means a
polymer consisting of several linear block chains linked together at one end
of each chain
by a single branch or junction point, also known as a radial block copolymer;
"End functionalized" means a polymer chain terminated with a functional group
on
at least one chain end; and
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"Polymeric matrix" means any resinous phase of a reinforced plastic material
in
which the additives of a composite are embedded.
Detailed Description
The polymeric matrix includes a plurality of microspheres, and one or more
block
copolymers in a compatible mixture. The block copolymers have at least one
segment that
is capable of interacting with the microspheres in the compatible mixture. The
interaction
involving at least one segment of the block copolymer and the microsphere is
capable of
enhancing or restoring mechanical properties of the polymeric matrix to
desirable levels in
comparison to polymeric matrices without the block copolymer.
Polymeric Matrix
The polymeric matrix is generally any thermoplastic or thermosetting polymer
or
copolymer upon which a block copolymer and microspheres may be employed. The
polymeric matrix includes both hydrocarbon and non-hydrocarbon polymers.
Examples of
useful polymeric matrices include, but are not limited to, polyamides,
polyimides,
polyethers, polyurethanes, polyolefins, polystyrenes, polyesters,
polycarbonates,
polyketones, polyureas, polyvinyl resins, polyacrylates, polymethylacrylates,
and
fluorinated polymers.
One preferred application involves melt-processable polymers where the
constituents are dispersed in melt mixing stage prior to formation of an
extruded or
molded polymer article.
For purposes of the invention, melt processable compositions are those that
are
capable of being processed while at least a portion of the composition is in a
molten state.
Conventionally recognized melt processing methods and equipment may be
employed in processing the compositions of the present invention. Non-limiting
examples
of melt processing practices include extrusion, injection molding, batch
mixing, rotation
molding, and pultrusion.
Preferred polymeric matrices include polyolefins (e.g., high density
polyethylene
(HDPE), low density polyethylene (LDPE), linear low density polyethylene
(LLDPE)
polypropylene (PP)), polyolefin copolymers (e.g., ethyleno-butene, ethylene-
octene,
ethylene vinyl alcohol), polystyrenes, polystyrene copolymers (e.g., high
impact
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polystyrene, acrylonitrile butadiene styrene copolymer), polyacrylates,
polymethacrylatq
polyesters, polyvinylchloride (PVC), fluoropolymers, liquid crystal polymers,
polyamides,
polyether imides, polyphenylene sulfides, polysulfones, polyacetals,
polycarbonates,
polyphenylene oxides, polyurethanes, thermoplastic elastomers, epoxies,
alkyds,
melamines, phenolics, ureas, vinyl esters or combinations thereof.
The polymeric matrix is included in a melt processable composition in amounts
typically greater than about 30% by weight. Those skilled in the art recognize
that the
amount of polymeric matrix will vary depending upon, for example, the type of
polymer,
the type of block copolymer, the processing equipment, processing conditions,
and the
desired end product.
Useful polymeric binders include blends of various polymers and blends thereof
containing conventional additives such as antioxidants, light stabilizers,
fillers,
antiblocking agents, plasticizers, fire retardants, and pigments. The
polymeric matrix may
be incorporated into the melt processable composition in the form of powders,
pellets,
granules, or in any other form.
Another preferred polymeric matrix includes pressure sensitive adhesives
(PSA).
These types of materials are well suited for applications involving
microspheres in
conjunction with block copolymers. Polymeric matrices suitable for use in
PSA's are
generally recognized by those of skill in the art and include those fully
described in U.S.
Patent Nos. 5,412,031, 5,502,103, 5,693,425, 5,714,548, herein incorporated by
reference
in their entirety. Additionally, conventional additives with PSA's, such as
tackifiers,
fillers, plasticizers, pigments fibers, toughening agents, fire retardants,
and antioxidants,
may also be included in the mixture.
Elastomers are another subset of polymers suitable for use as a polymeric
matrix.
Useful elastomeric polymeric resins (i.e., elastomers) include thermoplastic
and thermoset
elastomeric polymeric resins, for example, polybutadiene, polyisobutylene,
ethylene-
propylene copolymers, ethylene-propylene-diene terpolymers, sulfonated
ethylene-
propylene-diene terpolymers, polychloroprene, poly(2,3-dimethylbutadiene),
poly(butadiene-co-pentadiene), chlorosulfonated polyethylenes, polysulfide
elastomers,
silicone elastomers, poly(butadiene-co-nitrile), hydrogenated nitrile-
butadiene copolymers,
acrylic elastomers, ethylene-acry late copolymers.
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Useful thermoplastic elastomeric polymer resins include block copolymers, made
up of blocks of glassy or crystalline blocks such as, for example,
polystyrene,
poly(vinyltoluene), poly(t-butylstyrene), and polyester, and the elastomeric
blocks such as
polybutadiene, polyisoprene, ethylene-propylene copolymers, ethylene-butylene
copolymers, polyether ester and the like as, for example, poly(styrene-
butadiene-styrene)
block copolymers marketed by Shell Chemical Company, Houston, Texas, under the
trade
designation "KRATON". Copolymers and/or mixtures of these aforementioned
elastomeric polymeric resins can also be used.
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Useful polymeric matrices also include fluoropolymers, that is, at least
partially
fluorinated polymers. Useful fluoropolymers include, for example, those that
are
preparable (e.g., by free-radical polymerization) from monomers comprising 25
chlorotrifluoroethylene, 2-chloropentafluoropropene, 3-
chloropentafluoropropene,
vinylidene fluoride, trifluoroethylene, tetrafluoroethylene, 1-
hydropentafluoropropene, 2-
hydropentafluoropropene, 1,1-dichlorofluoroethylene, dichlorodifluoroethylene,
hexafluoropropylene, vinyl fluoride, a perfluorinated vinyl ether (e.g., a
perfluoro(alkoxy
vinyl ether) such as CF3OCF2CF2CF2OCF=CF2, or a perfluoro(alkyl vinyl ether)
such as
perfluoro(methyl vinyl ether) or perfluoro(propyl vinyl ether)), cure site
monomers such as
for example, nitrile containing monomers (e.g., CF2=CFO(CF2)LCN,
CF2=CFO[CF2CF(CF3)O]q(CF2O)YCF(CF3)CN, CF2=CF[OCF2CF(CF3)],O(CF2)tCN, or
CF2=CFO(CF2)õOCF(CF3)CN where L = 2-12; q = 0-4; r = 1-2; y = 0-6; t = 1-4;
and u =
2-6), bromine containing monomers (e.g., Z-Rf-Ox-CF=CFZ, wherein Z is Br or I,
Rf is a
substituted or unsubstituted C1-C12 fluoroalkylene, which may be
perfluorinated and may
contain one or more ether oxygen atoms, and x is 0 or 1); or a combination
thereof,
optionally in combination with additional non-fluorinated monomers such as,
for example,
ethylene or propylene. Specific examples of such fluoropolymers include
polyvinylidene
fluoride; copolymers of tetrafluoroethylene, hexafluoropropylene and
vinylidene fluoride;
copolymers of tetrafluoroethylene, hexafluoropropylene, perfluoropropyl vinyl
ether, and
vinylidene fluoride; tetrafluoroethylene-hexafluoropropylene copolymers;
tetrafluoroethylene-perfluoro(alkyl vinyl ether) copolymers (e.g.,
tetrafluoroethyleneperfluoro( propyl vinyl ether)); and combinations thereof.
Useful commercially available thermoplastic fluoropolymers include, for
example,
those marketed by Dyneon, LLC, Oakdale, Minnesota, under the trade
designations "THV"
(e.g., "THV 220", "THV 400G", "THV 500G", "THV 815", and "THV 610X"), "PVDF",
"PFA","HTE", "ETFE", and "FEP"; those marketed by Atofina Chemicals,
Philadelphia,
Pennsylvania, under the trade designation "KYNAR" (e.g., "KYNAR 740"); those
marketed by Solvay Solexis, Thorofare, New Jersey, under the trade
designations
"HYLAR" (e.g., "HYLAR 700") and "HALAR ECTFE".
Microspheres
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Conventional microspheres are employed with the composite of the present
invention. The microspheres may be any microsphere generally recognized by
those of
skill in the art as being suitable for use in a polymer matrix. The
utilization of
microspheres provides certain mechanical modifications, such as, improvements
in
strength to density ratios or shrinkage and warpage. The microspheres
preferably include
glass or ceramic materials and most preferably are hollow glass microspheres.
Non-
limiting examples of commercially available microsphere include 3MTM
ScotchliteTM
Glass Bubbles, 3MTM Z-LightTM Spheres Microspheres, and 3M TM Zeeospheres TM
Ceramic Microspheres from 3M Company St. Paul, MN.
Block Copolymers
The block copolymers are preferably compatible with the polymeric matrix. A
compatible mixture refers to a material capable of forming a dispersion in a
continuous
matrix of a second material, or capable of forming a co-continuous polymer
dispersion of
both materials. The block copolymers are capable of interacting with the
microspheres. In
one sense, and without intending to limit the scope of the present invention,
applicants
believe that the block copolymers may act as a coupling agent to the
microspheres in the
compatible mixture, as a dispersant in order to consistently distribute the
microspheres
throughout the compatible mixture, or both.
Preferred examples of block copolymers include di-block copolymers, tri-block
copolymers, random block copolymers, graft-block copolymers, star-branched
copolymers
or hyper-branched copolymers. Additionally, block copolymers may have end
functional
groups.
Block copolymers are generally formed by sequentially polymerizing different
monomers. Useful methods for forming block copolymers include, for example,
anionic,
cationic, coordination, and free radical polymerization methods.
The block copolymers interact with the microspheres through functional
moieties.
Functional blocks typically have one or more polar moieties such as, for
example, acids
(e.g., -C02H, -SO3H, -PO3H); -OH; -SH; primary, secondary, or tertiary amines;
ammonium N-substituted or unsubstituted amides and lactams; N-substituted or
unsubstituted thioamides and thiolactams; anhydrides; linear or cyclic ethers
and
polyethers; isocyanates; cyanates; nitriles; carbamates; ureas; thioureas;
heterocyclic
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amines (e.g., pyridine or imidazole)). Useful monomers that may be used to
introduce
such groups include, for example, acids (e.g., acrylic acid, methacrylic acid,
itaconic acid,
maleic acid, fumaric acid, and including methacrylic acid functionality formed
via the acid
catalyzed deprotection of t-butyl methacrylate monomeric units as described in
U.S. Pat.
Publ. No. 2004/0024130 (Nelson et al.)); acrylates and methacrylates (e.g., 2-
hydroxyethyl
acrylate), acrylamide and methacrylamide, N-substituted and N,N-disubstituted
acrylamides (e.g., N-t-butylacrylamide, N,N-(dimethylamino)ethylacrylamide,
N,N-
dimethylacrylamide, N,N-dimethylmethacrylamide), N-ethylacrylamide, N-
hydroxyethylacrylamide, N-octylacrylamide, N-t-butylacrylamide, N,N-
dimethylacrylamide, N,N-diethylacrylamide, and N-ethyl-N-
dihydroxyethylacrylamide),
aliphatic amines (e.g., 3-dimethylaminopropyl amine, N,N-
dimethylethylenediamine); and
heterocyclic monomers (e.g., 2-vinylpyridine, 4-vinylpyridine, 2-(2-
aminoethyl)pyridine,
1-(2-aminoethyl)pyrrolidine, 3-aminoquinuclidine, N-vinylpyrrolidone, and N-
vinylcaprolactam).
Other suitable blocks typically have one or more hydrophobic moieties such as,
for
example, aliphatic and aromatic hydrocarbon moieties such as those having at
least about
4, 8, 12, or even 18 carbon atoms; fluorinated aliphatic and/or fluorinated
aromatic
hydrocarbon moieties, such as, for example, those having at least about 4, 8,
12, or even 18
carbon atoms; and silicone moieties.
Non-limiting examples of useful monomers for introducing such blocks include:
hydrocarbon olefins such as ethylene, propylene, isoprene, styrene, and
butadiene; cyclic
siloxanes such as decamethylcyclopentasiloxane and decamethyltetrasiloxane;
fluorinated
olefins such as tetrafluoroethylene, hexafluoropropylene, trifluoroethylene,
difluoroethylene, and chlorofluoroethylene; nonfluorinated alkyl acrylates and
methacrylates such as butyl acrylate, isooctyl methacrylate lauryl acrylate,
stearyl acrylate;
fluorinated acrylates such as perfluoroalkylsulfonamidoalkyl acrylates and
methacrylates
having the formula H2C=C(R2)C(O)O-X-N(R)SO2Rf' wherein: Rl' is -C6F13, -C4F9,
or
-C3F7; R is hydrogen, C 1 to C 10 alkyl, or C6-C 10 aryl; and X is a divalent
connecting
group. Preferred examples include
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C4F9SO2N(CH3)C2H4OC(O)NH(C6H4)CH2C6H4NHC(O)OC2H4OC(O)CH=CH2 or
C4F9SO2N(CH3)C2H4OC(O)NH(C6H4)CH2C6H4NH
C(O)OC2H4OC(O)C(CH3)=CH2 .
Such monomers may be readily obtained from commercial sources or prepared, for
example, according to the procedures in U.S. Pat. Appl. Publ. No. 2004/0023016
(Cernohous et al.), the disclosure of which is incorporated herein by
reference.
Other non-limiting examples of useful block copolymers having functional
moieties include poly(isoprene-block-4-vinylpyridine); poly(isoprene-block-
methacrylic
acid); poly(isoprene-block-N,N-(dimethylamino)ethyl acrylate); poly(isoprene-
block-2-
diethylaminostyrene); poly(isoprene-block-glycidyl methacrylate);
poly(isoprena-block-2-
hydroxyethyl methacrylate); poly(isoprene-block-N-vinylpyrrolidone);
poly(isoprene-
block-methacrylic anhydride); poly(isoprene-block-(methacrylic anhydride-co-
methacrylic
acid)); poly(styrene-block-4-vinylpyridine); poly(styrene-block-2-
vinylpyridine);
poly(styrene-block-acrylic acid); poly(styrene-block-methacrylamide);
poly(styrene-block-
N-(3-aminopropyl)methacrylamide); poly(styrena-block-N,N-(dimethylamino)ethyl
acrylate); poly(styrene-block-2-diethylaminostyrene); poly(styrene-block-
glycidyl
methacrylate); poly(styrene-block-2-hydroxyethyl methacrylate);
poly(styrene=block-N-
vinylpyrrolidone copolymer); poly(styreno-block-isoprene-block-4-
vinylpyridine);
poly(styrene-block-isoprene-block-glycidyl methacrylate); poly(styrene-block-
isoprene-
block-methacrylic acid); poly(styrene-block-isoprene-block-(methacrylic
anhydride-co-
methacrylic acid)); poly(styrene-block-isoprene-block-methacrylic anhydride);
poly(butadiene-block-4-vinylpyridine); poly(butadiene-block-methacrylic acid);
poly(butadiene-block-N,N-(dimethylamino)ethyl acrylate); poly(butadiena-block-
2-
diethylaminostyrene); poly(butadiene-block-glycidyl methacrylate);
poly(butadiene-block-
2-hydroxyethyl methacrylate); poly(butadiene-block-N-vinylpyrrolidone);
poly(butadiene-
block- methacrylic anhydride); poly(butadien~block-(methacrylic anhydride-co-
methacrylic acid); poly(styrene-block-butadiene-block-4-vinylpyridine);
poly(styrene-
block-butadiene-block-methacrylic acid); poly(styreno-block-butadiene-block-
N,N-
(dimethylamino)ethyl acrylate); poly(styrenablock-butadiene-block-2-
diethylaminostyrene); poly(styrene -block-butadiene-block-glycidyl
methacrylate);
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poly(styrene-block-butadiene-block-2-hydroxyethyl methacrylate); poly(styrene-
block-
butadiene-block-N-vinylpyrrolidone); poly(styrene-block-butadiene-block-
methacrylic
anhydride); poly(styrene-block-butadiene-block-(methacrylic anhydride-co-
methacrylic
acid)); and hydrogenated forms of poly(butadiene-block-4-vinylpyridine),
poly(butadiene-
block-methacrylic acid), poly(butadiene-block-N,N-(dimethylamino)ethyl
acrylate),
poly(butadiene-block-2-diethylaminostyrene), poly(butadiene-block-glycidyl
methacrylate), poly(butadiene-block-2-hydroxyethyl methacrylate),
poly(butadiene-block-
N-vinylpyrrolidone), poly(butadiene-block-methacrylic anhydride),
poly(butadiene-block-
(methacrylic anhydride-co-methacrylic acid)), poly(i soprene-bl ock-4-viny
lpyri dine),
poly(isoprene-block-methacrylic acid), poly(isoprene-block-N,N-
(dimethylamino)ethyl
acrylate), poly(isoprene-block-2-diethylaminostyrene), poly(isoprene-block-
glycidyl
methacrylate), poly(isoprene-block-2-hydroxyethyl methacrylate), polAisoprene-
block-N-
vinylpyrrolidone), poly(isoprene-block-methacrylic anhydride), poly(isoprene-
block-
(methacrylic anhydride-co-methacrylic acid)), poly(styrene-block-isoprene-
block-glycidyl
methacrylate), poly(styrene-block-isoprene-block-methacrylic acid),
poly(styrene-block-
isoprene-block-methacrylic anhydride-co-methacrylic acid), styrene-block-
isoprene-block-
methacrylic anhydride, poly(styreno-block-butadiene-block-4-vinylpyridine),
poly(styrene-
block-butadiene-block- methacrylic acid), poly(styrene-block-butadiene-block-
N,N-
(dimethylamino)ethyl acrylate), poly(styrena-block-butadiene-block-2-
diethylaminostyrene), poly(styrene -block-butadiene-block-glycidyl
methacrylate),
poly(styrene-block-butadiene-block-2-hydroxyethyl methacrylate),
poly(styrenablock-
butadiene-block-N-vinylpyrrolidone), poly(styrene-block-butadiene-block-
methacrylic
anhydride), poly(styrene-block-butadiene-block-(methacrylic anhydride-co-
methacrylic
acid), poly(MeFBSEMA-block-methacrylic acid) (wherein "MeFBSEMA" refers to 2-
(N-
methylperfluorobutanesulfonamido)ethyl methacrylate, e.g., as available from
3M
Company, Saint Paul, Minnesota), poly(MeFBSEMA-block-t-butyl methacrylate),
poly(styrene-block-t-butyl methacrylate-block-MeFBSEMA), poly(styrene-block-
methacrylic anhydride-block-MeFBSEMA), poly(styrene-block- methacrylic acid-
block-
MeFBSEMA), poly(styrene-block-(methacrylic anhydride-co-methacrylic acid)-
block-
MeFBSEMA)), poly(styrene-block-(methacrylic anhydride-co-methacrylic acid-co-
MeFBSEMA)), poly(styrene-block-(t-butyl methacrylate-co-MeFBSEMA)),
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poly(styrene-block-isoprene-block-t-butyl methacrylate-block-MeFBSEMA),
poly(styrene-
isoprene-block-methacrylic anhydride-block-MeFBSEMA), poly(styrene-isoprene-
block-
methacrylic acid-block-MeFBSEMA), poly(styrene-block-isoprene-block-
(methacrylic
anhydride-co-methacrylic acid)-block-MeFBSEMA), poly(styrene-block-isoprene-
block-
(methacrylic anhydride-co-methacrylic acid-co-MeFBSEMA)), poly(styrene-block-
isoprene-block-(t-butyl methacrylate-co-MeFB SEMA)), poly(MeFB SEMA-block-
methacrylic anhydride), poly(MeFBSEMA-block-(methacrylic acid-co-methacrylic
anhydride)), poly(styrene-block-(t-butyl methacrylate-co-MeFBSEMA)),
poly(styrene-
block-butadiene-block-t-butyl methacrylate-block-MeFBSEMA), poly(styrene-
butadiene-
block-methacrylic anhydride-block-MeFBSEMA), poly(styrene-butadiene-block-
methacrylic acid-block-MeFBSEMA), poly(styrene-block- butadiene-block-
(methacrylic
anhydride-co-methacrylic acid)-block-MeFBSEMA), poly(styrene-block-butadiene-
block-
(methacrylic anhydride-co-methacrylic acid-co-MeFBSEMA)), and poly(styrene-
block-
butadiene-block-(t-butyl methacrylate-co-MeFBSEMA)).
Generally, the block copolymer should be chosen such that at least one block
is
capable of interacting with the microspheres. The choice of remaining blocks
of the block
copolymer will typically be directed by the nature of any polymeric resin with
which the
block copolymer will be combined.
The block copolymers may be end-functionalized polymeric materials that can be
synthesized by using functional initiators or by end-capping living polymer
chains, as
conventionally recognized in the art. The end-functionalized polymeric
materials of the
present invention may comprise a polymer terminated with a functional group on
at least
one chain end. The polymeric species may be homopolymers, copolymers, or block
copolymers. For those polymers that have multiple chain ends, the functional
groups may
be the same or different. Non-limiting examples of functional groups include
amine,
anhydride, alcohol, carboxylic acid, thiol, maleate, silane, and halide. End-
functionalization strategies using living polymerization methods known in the
art can be
utilized to provide these materials.
Any amount of block copolymer may be used, however, typically the block
copolymer is included in an amount in a range of up to 5% by weight.
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Coupling Agents
In a preferred embodiment, the microspheres may be treated with a coupling
agent
to enhance the interaction between the microspheres and the block copolymer.
It is
desirable to select a coupling agent that matches or provides suitable
reactivity with
corresponding functional groups of the block copolymer. Non-limiting examples
of
coupling agents include zirconates, silanes, or titanates. Typical titanate
and zirconate
coupling agents are known to those skilled in the art and a detailed overview
of the uses
and selection criteria for these materials can be found in Monte, S.J.,
Kenrich
Petrochemicals, Inc., "Ken-React Reference Manual - Titanate, Zirconate and
Aluminate
Coupling Agents", Third Revised Edition, March, 1995. The coupling agents are
included
in an amount of about 1 to 3% by weight.
Suitable silanes are coupled to glass surfaces through condensation reactions
to
form siloxane linkages with the siliceous filler. This treatment renders the
filler more
wettable or promotes the adhesion of materials to the glass surface. This
provides a
mechanism to bring about covalent, ionic or dipole bonding between inorganic
fillers and
organic matrices. Silane coupling agents are chosen based on the particular
functionality
desired. For example, an aminosilane glass treatment may be desirable for
compounding
with a block copolymer containing an anhydride, epoxy or isocyanate group.
Alternatively, silane treatments with acidic functionality may require block
copolymer
selections to possess blocks capable of acid-base interactions, ionic or
hydrogen bonding
scenarios. Another approach to achieving intimate glass microsphere-block
copolymer
interactions is to functionalize the glass microsphere with a suitable
coupling agent that
contains a polymerizable moiety, thus incorporating the material directly into
the polymer
backbone. Examples of polymerizable moieties are materials that contain
olefinic
functionality such as styrenic, acrylic and methacrylic moieties. Suitable
silane coupling
strategies are outlined in Silane Coupling Agents: Connecting Across
Boundaries, by
Barry Arkles, pg 165 - 189, Gelest Catalog 3000-A Silanes and Silicones:
Gelest Inc.
Morrisville, PA. Those skilled in the art are capable of selecting the
appropriate type of
coupling agent to match the block copolymer interaction site.
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The combination of block copolymers with microspheres in a polymeric composite
may enhance certain mechanical properties of the composite, such as tensile
strength,
impact resistance, tensile modulus, and flexural modulus. In a preferred
embodiment, the
composition exhibits a maximum tensile strength value within 25% of the
maximum
tensile strength value of the pure polymer matrix. More preferably, the
maximum tensile
strength value is within 10% of the maximum tensile strength value of the pure
polymer
matrix, and even more preferably is within 5%.
The improved physical characteristics render the composites of the present
invention suitable for use in many varied applications. Non-limiting examples
include,
automotive parts (e.g., o-rings, gaskets, hoses, brake pads, instrument
panels, side impact
panels, bumpers, and fascia), molded household parts, composite sheets,
thermoformed
parts.
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Examples
Table 1: Materials
Material Description
PP 3825 Atofina 3825 - 30 MFI polypropylene, Available from Atofina
Petrochemicals, Houston, TX
PP 1024 Escorene 1024 12 MFI polypropylene, commercially available from
ExxonMobil, Irving, TX
An AB diblock copolymer, poly[isoprene-b-methacrylic acid].
P(I-MAA) Synthesized using a stirred tubular reactor process as described in
US 6,448,353. Mõ = 70 kg/mol, PD1=1.8, 80/20 PI/MAA by
weight
An ABC triblock copolymer, poly[styrene-b-isoprene-b-methacrylic
P(S-I-MAn) anhydride]. Synthesized using a stirred tubular reactor process as
described in US 6,448,353. Mõ = 70 kg/mol, PDI =1.5, 15/55/30
PS/PI/MAn by weight
P(EP-MAn) An AB diblock copolymer, poly[ethylene-co-propylene-b-
methacrylic acid-co-anhydride]. The precursor of this block
copolymer (poly(isoprene - b - t-butyl methacrylate) was
synthesized using a stirred tubular reactor process as described in
US 6,448,253. The polymer was hydrogenated to -50% and
functionalized according to US20040024130. Mn = 40 kg/mol,
PD1=1. 8, 90/10 PEP/MAn by wei ht
3M ScotchliteTM Glass Bubbles S60HS with an average diameter
S60HS of 30 m and a 10% isostatic collapse -strength of 19,000 psi,
Commercially available from 3M, St. Paul, MN
S80HP 3M Experimental Glass Bubble S80HP with and average diameter
of 18 m and a 10% isostatic collapse strength of 29,000psi
Glass Fiber Cratec 123D chopped glass fiber, Commercially available from
Owens Cornin , Toledo, OH
Batch Composite Formation
A Brabender Torque Rheometer Model PL2100 with a Type 6 mixer head utilizing
roller blade mixing paddles was used to compound the microsphere-composites.
For all
samples, the brabender was heated to 180 C and mixed at a paddle speed of 50
rpm. The
polymeric matrices was initially melted in the brabender and the temperature
was allowed
to equilibrate. Once a steady melt temperature was reached, microspheres and
the block
copolymer additive (if used) were added simultaneously. The temperature was
allowed to
equilibrate once more and the composite was mixed for an additional 5 minutes.
The resultant composite was placed between 2mil thick untreated polyester
liners,
which were placed between 2 aluminum plates (1/8 inch thick each) to form a
stack. Two
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shims (1 mm thick) were placed to either side of the mixture between the
liners such that
upon pressing the assembled stack the mixture would not come into contact with
either
shim. This stack of materials was placed in a hydraulic press (Wabash MPI
model G30H-
15-LP). Both the top and bottom press plates were heated to 193 C. The stack
was
pressed for 1 minute at 1500psi. The hot stack was then moved to a low-
pressure water-
cooled press for 30 seconds to cool the stack. The stack was disassembled and
the liners
were removed from both sides of the film disc that resulted from pressing the
mixture.
Physical Property Testing
Tensile bars were stamped out of the composite films produced according to
ASTM D1708. The samples were tested on an Instron 5500 R tensile tester
(available
from Instron Corporation, Canton, MA). They were pulled at a rate of 50.8
mm/min in a
temperature and humidity controlled room at 21.1 C and 55% relative humidity.
For each
sample, 5 specimens were tested and a mean value for the maximum Tensile
Strength was
calculated.
PP/ microsphere composites were made according to the general procedure for
Batch Composite Formation. P(EP-MAn) was utilized as a coupling agent and
compared
to those samples prepared with only microspheres. The compositions and
resulting tensile
stress measurements are shown in Table 2.
Table 2: Example 1 feed compositions and sample tensile strength
Sample PP 3825__T S60HS (g) P(EP-MAn) (g) Max Tensile Stress
ID (g) (MPa)
1A Not Processed 0.0 0 30.6
1 B 175.0 35.0 0 20.3
1 C 175.0 35.0 5.3 26.6
As shown in Table 2, the addition of microspheres has a detrimental effect on
the
tensile strength of PP. Adding just 2.5% of a block copolymer results in an
increase in
tensile strength of the microsphere-filled composite.
Example 2
Continuous Composite Formation
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Polypropylene composites were compounded using a 19 mm, 15:1 L:D, Haake
Rheocord Twin Screw Extruder (commercially available from Haake Inc.,
Newington,
NH). The extruder was equipped with a conical counter-rotating screw and the
raw
materials were dry-blended and fed with an Accurate open helix dry material
feeder
(commercially available from Accurate Co. Whitewater, WI). The extrusion
parameters
were controlled and experimental data recorded using the Haake RC 9000 control
data
computerized software (commercially available for Haake Inc., Newington, NH).
Materials were extruded through a standard 0.05 cm diameter, 4-strand die
(commercially
available from Haake Inc., Newington, NH). The sample compositions are shown
in Table
3.
Table 3: Example 2 Compositions
Sample ID PP 1024 Glass fiber S60HS S80HP P(I-MAA) P S-I-MAn
2A Control 80.0% 10.0% 0.0% 10.0% 0.0% 0.0%
2B 78.0% 10.0% 0.0% 10.0% 2.0% 0.0%
2C 78.0% 10.0% 0.0% 10.0% 0.0% 2.0%
2D 75.0% 10.0% 0.0% 10.0% 5.0% 0.0%
2E 75.0% 10.0% 0.0% 10.0% 0.0% 5.0%
2F Control 80.0% 10.0% 10.0% 0.0% 0.0% 0.0%
2G 78.0% 10.0% 10.0% 0.0% 2.0% 0.0%
2H 78.0% 10.0% 10.0% 0.0% 0.0% 2.0%
21 75.0% 10.0% 10.0% 0.0% 5.0% 0.0%
2J 75.0% 10.0% 10.0% 0.0% 0.0% 5.0%
2K Control 80.0% 10.0% 5.0% 5.0% 0.0% 0.0%
2L 78.0% 10.0% 5.0% 5.0% 2.0% 0.0%
2M 78.0% 10.0% 5.0% 5.0% 0.0% 2.0%
2N 75.0% 10.0% 5.0% 5.0% 5.0% 0.0%
75.0% 10.0% 5.0% 5.0% 0.0% 5.0%
The resulting pellets were injection molded into tensile bars using a
Cincinnati-
15 Milacron-Fanuc Roboshot I10 R injection molding apparatus equipped with a
series 16-I
control panel (commercially available from Milacron Inc., Batavia, Ohio. The
samples
were injection molded according to 3M Glass Bubbles Compounding and Injection
Molding Guidelines, available at http://www.3m.com/.
Tensile bars for physical property testing were made according to ASTM D 1708.
20 The samples were tested on an Instron 5500 R tensile tester (available from
Instron
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Corporation, Canton, MA). They were pulled at a rate of 50.8 mm/min in a
temperature
and humidity controlled room at 21.1 C and 55% relative humidity. For each
sample, 5
specimens were tested and the tensile modulus and tensile stress were
calculated. Physical
property results for Example 2 are shown in Table 4.
Table 4: Physical Property Results for Example 2
Tensile Modulus (MPa) Max Tensile Stress (MPa)
Sample ID Mean S.D. Mean S.D.
2A Control 1587.3 111.0 34.0 0.4
2B 1990.6 161.4 40.2 0.8
2C 1816.6 100.7 40.8 0.2
2D 2087.9 209.3 44.4 1.0
2E 1799.3 111.1 40.3 0.7
2F Control 1557.0 52.6 34.1 0.5
2G 2078.8 117.6 45.0 1.1
2H 1811.9 83.1 41.6 0.4
21 2004.3 133.0 45.4 0.7
2J 1806.1 71.2 42.8 0.5
2K Control 1869.6 117.7 33.7 0.6
2L 1959.3 122.5 36.3 0.3
2M 1965.4 23.3 42.8 0.7
2N 1887.5 96.4 40.8 2.0
20 1782.2 144.0 41.3 0.8
With both block copolymer additives, P(I-MAA) and P(S-I-MAn), the max tensile
stress and tensile modulus are consistently higher than the controls with no
additives. The
additive is effective for both sizes of hollow glass microspheres and
combinations of the
two.
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